PRELIMINARY INFORMATION ON THE ENDOCRANIAL MORPHOLOGY OF THE TYPE SPECIMEN OF “PRODOLICHOTIS” PRIDIANA (RODENTIA, HYSTRICOGNATHI, CAVIOIDEA), FROM THE MIDDLE MIOCENE OF LA VENTA (COLOMBIA)

PEREZ, M.A.; PAULINA CARABAJAL, A.; FLYNN, J.

VIRTUAL

Congreso; Reunión de Comunicaciones de la Asociación Paleontologica Argentina; 2021

Asociacion Paleontologica Argentina

Caviomorphs are a diverse group of South American rodents exhibiting broad ecological and morphological diversity, and variable habits. Between them, the cavioid “Prodolichotis” pridiana from the middle Miocene of La Venta (Colombia) is the sister-group of the striking Caviidae (current maras, capybaras, and guinea-pig relatives). A microCT scan of the skull of the holotype specimen (uCMP 38761) allowed the first reconstruction of the brain and inner ear, and also the recovery of two ossicles of the middle ear for this taxon. The brain endocast shows separation between the olfactory bulbs and the cerebral hemispheres. The sagittal sinus and the deep lateral sulci run throughout the total length of the cerebral hemispheres. The cerebellum is represented by the central vermis and two lateral cerebellar hemispheres, separated by well-marked paramedian fissures; the paraflucculus is evident. Comparisons with other extinct and extant rodents are limited to few closely related taxa. The living Dolichotis patagonum and the extict Prodolichotis prisca share with “P ” . pridiana the brain outline in dorsal view (which does not narrow abruptly anteriorly), and the presence of deep and long lateral sulci. The suprasylvian sulcus in our specimen is less noticeable. Within Caviidae, the brain morphology of “P ” . pridiana is more similarto that in Caviinae than that in Hydrocheoerus. The inner ear morphology highly resembles that in other caviomorphs. The malleus and incus are fused, as in other rodents, and are highly similar to those of Dolichotis, although the mallear head is relatively more elongated in the extinct form.